CURLOPT_DEBUGFUNCTION(3)   curl_easy_setopt options   CURLOPT_DEBUGFUNCTION(3)

NAME
       CURLOPT_DEBUGFUNCTION - debug callback

SYNOPSIS
       #include <curl/curl.h>

       typedef enum {
         CURLINFO_TEXT = 0,
         CURLINFO_HEADER_IN,    /* 1 */
         CURLINFO_HEADER_OUT,   /* 2 */
         CURLINFO_DATA_IN,      /* 3 */
         CURLINFO_DATA_OUT,     /* 4 */
         CURLINFO_SSL_DATA_IN,  /* 5 */
         CURLINFO_SSL_DATA_OUT, /* 6 */
         CURLINFO_END
       } curl_infotype;

       int debug_callback(CURL *handle,
                          curl_infotype type,
                          char *data,
                          size_t size,
                          void *userptr);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEBUGFUNCTION,
                                 debug_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the proto-
       type shown above.

       CURLOPT_DEBUGFUNCTION(3) replaces the standard debug function used when
       CURLOPT_VERBOSE(3)  is in effect. This callback receives debug informa-
       tion, as specified in the type argument. This function must  return  0.
       The  data  pointed to by the char * passed to this function WILL NOT be
       zero terminated, but will be exactly of the size as told  by  the  size
       argument.

       The userptr argument is the pointer set with CURLOPT_DEBUGDATA(3).

       Available curl_infotype values:

       CURLINFO_TEXT
              The data is informational text.

       CURLINFO_HEADER_IN
              The data is header (or header-like) data received from the peer.

       CURLINFO_HEADER_OUT
              The data is header (or header-like) data sent to the peer.

       CURLINFO_DATA_IN
              The data is protocol data received from the peer.

       CURLINFO_DATA_OUT
              The data is protocol data sent to the peer.

       CURLINFO_SSL_DATA_OUT
              The data is SSL/TLS (binary) data sent to the peer.

       CURLINFO_SSL_DATA_IN
              The data is SSL/TLS (binary) data received from the peer.

DEFAULT
       NULL

PROTOCOLS
       All

EXAMPLE
       static
       void dump(const char *text,
                 FILE *stream, unsigned char *ptr, size_t size)
       {
         size_t i;
         size_t c;
         unsigned int width=0x10;

         fprintf(stream, "%s, %10.10ld bytes (0x%8.8lx)\n",
                 text, (long)size, (long)size);

         for(i=0; i<size; i+= width) {
           fprintf(stream, "%4.4lx: ", (long)i);

           /* show hex to the left */
           for(c = 0; c < width; c++) {
             if(i+c < size)
               fprintf(stream, "%02x ", ptr[i+c]);
             else
               fputs("   ", stream);
           }

           /* show data on the right */
           for(c = 0; (c < width) && (i+c < size); c++) {
             char x = (ptr[i+c] >= 0x20 && ptr[i+c] < 0x80) ? ptr[i+c] : '.';
             fputc(x, stream);
           }

           fputc('\n', stream); /* newline */
         }
       }

       static
       int my_trace(CURL *handle, curl_infotype type,
                    char *data, size_t size,
                    void *userp)
       {
         const char *text;
         (void)handle; /* prevent compiler warning */
         (void)userp;

         switch (type) {
         case CURLINFO_TEXT:
           fprintf(stderr, "== Info: %s", data);
         default: /* in case a new one is introduced to shock us */
           return 0;

         case CURLINFO_HEADER_OUT:
           text = "=> Send header";
           break;
         case CURLINFO_DATA_OUT:
           text = "=> Send data";
           break;
         case CURLINFO_SSL_DATA_OUT:
           text = "=> Send SSL data";
           break;
         case CURLINFO_HEADER_IN:
           text = "<= Recv header";
           break;
         case CURLINFO_DATA_IN:
           text = "<= Recv data";
           break;
         case CURLINFO_SSL_DATA_IN:
           text = "<= Recv SSL data";
           break;
         }

         dump(text, stderr, (unsigned char *)data, size);
         return 0;
       }

       int main(void)
       {
         CURL *curl;
         CURLcode res;

         curl = curl_easy_init();
         if(curl) {
           curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, my_trace);

           /* the DEBUGFUNCTION has no effect until we enable VERBOSE */
           curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

           /* example.com is redirected, so we tell libcurl to follow redirection */
           curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

           curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/");
           res = curl_easy_perform(curl);
           /* Check for errors */
           if(res != CURLE_OK)
             fprintf(stderr, "curl_easy_perform() failed: %s\n",
                     curl_easy_strerror(res));

           /* always cleanup */
           curl_easy_cleanup(curl);
         }
         return 0;
       }

AVAILABILITY
       Always

RETURN VALUE
       Returns CURLE_OK

SEE ALSO
       CURLOPT_VERBOSE(3), CURLOPT_DEBUGDATA(3),

libcurl 7.54.0                 October 06, 2016       CURLOPT_DEBUGFUNCTION(3)